GT4 shipments are at 10.18M.
Is Polyphony Digital a good enough source?
http://www.polyphony.co.jp/english/list.html
That is "shipments", which is why it's a better number. "Shipments" are often more accurate than "sales" on a long enough timeline. This is because it is easier for one company to track what they've shipped than to add up a bunch of retail sales *estimates* from all sorts of different sources, especially for a game that will sell 100s of Ks in smaller, poorly tracked European markets. Want to subtract 100K for "copies on shelves"? Go ahead. But don't pretend there's almost 700K "copies on shelves."
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
